Two-piece cans are the most common type of metal containers used in the beer and beverage industry. They are usually formed of aluminum or tin-plated steel. The two-piece can consists of a first cylindrical can body portion having an integral bottom end wall and a second, separately-formed, top end panel portion which, after the can has been filled, is double-seamed thereon to close the open upper end of the container.
An important competitive objective is to reduce the total can weight as much as possible while maintaining its strength and performance in accordance with industry requirements. For pressurized contents such as soft drinks or beer, the end panel must be made of a metal thickness gauge that is on the order of at least twice the thickness of the side wall. Accordingly, to minimize the overall container weight the second end panel should be diametrically as small as possible and yet maintain the structural integrity of the container, the functionality of the end, and also the aesthetically-pleasing appearance of the can.
Beer and beverage marketers have preferred a neck construction having a relatively smooth neck shape between the opening and the diameter can body sidewall. This smooth can neck construction was made by a spin necking process, and apparatus as shown, for example, in U.S. Pat. Nos. 4,058,998 and 4,512,172.
More recently, U.S. Pat. No. 5,497,900 described a die necking method for necking can bodies. The method of the '900 patent contemplates forming a cylindrical neck portion adjacent the cylindrical open end of a container so that the cylindrical neck merged with the cylindrical side wall through a generally smoothly tapered neck portion. The tapered neck portion between the cylindrical neck portion and the cylindrical container side wall initially is defined by a lower, generally arcuate segment having a relatively large internal curvature at the upper end of the cylindrical side wall and an upper, generally arcuate segment having a relatively large external curvature at the lower end of the reduced cylindrical neck. A further tapered portion is then formed at the open end and is forced downwardly while the cylindrical neck is further reduced. The further tapered portion freely integrates with the second arcuate segment which is reformed and the tapered portion is extended. This process is repeated sequentially until the cylindrical neck is reduced to the desired diameter and a smoothly tapered necked-in portion is formed on the end of the side wall. In each necking operation, the tapered portion is not constrained by the die and is freely formed without regard to the specific dimensions of the die transition zone.
The container that is formed by the above die necking process has an aesthetically-pleasing appearance, greater strength and crush resistance and is devoid of the scratches or wrinkles in the neck produced in a spin necking operation. Similar methods are still used today.
More recently, metal beer and beverage containers have produced metal cans to resemble glass bottles. U.S. Pat. Nos. 5,293,765 and 5,822,843 disclose methods and apparatuses for manufacturing threaded aluminum containers which resemble bottles.
One of the drawbacks of producing metal bottles is that the container manufacturer must build new facilities to produce the metal bottle or retrofit current facilities with new tooling to manufacture the metal bottles. Furthermore, the metal bottles are purported to use more than three times the metal used to make an aluminum can.
The present invention is provided to solve the problems discussed above and other problems, and to provide advantages and aspects not provided by prior metal bottles of this type. A full discussion of the features and advantages of the present invention is deferred to the following detailed description, which proceeds with reference to the accompanying drawings.